I received a popup asking me to update and I updated the software.It asked me to restart my computer after the update and I restarted it.Then it keeps restarting after the Windows logo and doesn't allow me to log in to any Windows accounts.I am using Windows XP and avast! Free.Any suggestions?

I managed to get in the Safe mode and uninstall avast!But now I am surfing the internet with any anti virus software and I am feeling unsafe.

@kevinpang, for XP you should be using at least SP3 and have Windows validated / registered before installing / updating Avast.

This is NOT a strict condition (specially for previous versions of Avast), and it is NOT a "solution" to the problem, but it seems that some users are having this type of problem with the latest updates of Avast, and the "workaround" might help you.

In any case (independently of Avast), it is recommended to have XP SP3 installed if you still haven't.

I have had the same problem since the Avast's "special update" that popped out on my screen on June 21, 2011 and I strongly believe that it is something wrong with that update. It was not the automatic usual daily message, it was different even in color. I clicked to install that "special update" and when I was asked to re-start the computer it kept on trying to load Windows time after time with a blue screen. I had to do a Windows Repair and, since Avast was not working after that, I uninstalled it and Windows loaded correctly. I re-installed Avast from its web site, and I was not able to open any program, not even the browser. I uninstalled Avast and Windows worked normally. I have been using Avast Free software for one year without problems while using Windows XP Pack 1. Today I updated my computer to Pack 3, but I am afraid to re-install Avast since I am convinced that it is something wrong with that update, not with the Pack number.It is unfortunate, but I will have to look for another anti-virus unless someone looks into this trouble. Thank you.

westsunrise, now that you have updated to SP3 why not give avast another try! you might be pleasantly surprised If you check the sig's of the other user's you will notice that there are plenty of xp user's with no issues, it pay's to always keep your system clean with something like ccleaner and always updated with the latest from windows updates and any other programs you may be running.